Re: [PATCH v11 00/23] x86/resctrl : Support AMD Assignable Bandwidth Monitoring Counters (ABMC)

[Moger, Babu]

[AMD Official Use Only - AMD Internal Distribution Only]

Hi Tony,

On 3/13/2025 3:36 PM, Luck, Tony wrote:
> On Thu, Mar 13, 2025 at 03:13:32PM -0500, Moger, Babu wrote:
>> Hi Reinette,
>>
>> On 3/13/25 11:08, Reinette Chatre wrote:
>>> Hi Babu,
>>>

>>>> #echo mbm_read_only > test/mon_data/mon_L3_00/assign_exclusive
>>>>
>>>> Which would result in the creation of test/mon_data/mon_L3_*/mbm_read_only
>>>>
>>>> So, there is not breakage of backword compatibility.
>>>
>>> The way I understand it I am seeing many incompatibilities. Perhaps I am missing
>>> something. Could you please provide detailed steps of how first phase and
>>> second phase would look?
>>
>> No. You didn't miss anything. I misspoke on few steps.
>>
>> Here are the steps. Just copying steps from Peters proposal.
>> https://lore.kernel.org/lkml/CALPaoCiii0vXOF06mfV=kVLBzhfNo0SFqt4kQGwGSGVUqvr2Dg@xxxxxxxxxxxxxx/
>>
>>
>> 1. Mount the resctrl
>>     mount -t resctrl resctrl /sys/fs/resctrl
>>
>> 2. When ABMC is supported two default configurations will be created.
>>
>>    a. info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>>    b. info/L3_MON/counter_configs/mbm_local_bytes/event_filter
>>
>>    These files will be populated with default total and local events
>>    # cat info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>>      VictimBW
>>      RmtSlowFill
>>      RmtNTWr
>>      RmtFill
>>      LclFill
>>      LclNTWr
>>      LclSlowFill
>>
>>    # cat info/L3_MON/counter_configs/mbm_local_bytes/event_filter
>>     LclFill,
>>     LclNTWr
>>     LclSlowFill
>>
>> 3. Users will have options to update the event configuration.
>>     echo LclFill > info/L3_MON/counter_configs/mbm_local_bytes/event_filter
>
> Once the "mkdir" support described below is implemented users will not
> need to redefine these legacy event file names. That makes me happy.

Yea. That is correct.

>
>>
>> 4. As usual the events can be read from the mon_data directories.
>>     #mkdir /sys/fs/resctrl/test
>>     #cd   /sys/fs/resctr/test
>>     #cat  test/mon_data/mon_data/mon_L3_00/mbm_tota_bytes
>>     101010
>>     #cat   test/mon_data/mon_data/mon_L3_00/mbm_local_bytes
>>     32323
>>
>> 5. There will be 3 files created in each group's mon_data directory when
>> ABMC is supported.
>>
>>     a. test/mon_data/mon_L3_00/assign_exclusive
>>     b. test/mon_data/mon_L3_00/assign_shared
>>     c. test/mon_data/mon_L3_00/unassign
>>
>>
>> 6. Events can be assigned/unassigned by these commands
>>
>>   # echo mbm_total_bytes > test/mon_data/mon_L3_00/assign_exclusive
>>   # echo mbm_local_bytes > test/mon_data/mon_L3_01/assign_exclusive
>>   # echo mbm_local_bytes > test/mon_data/mon_L3_01/unassign
>>
>>
>> Note:
>> I feel 3 files are excessive here. We can probably achieve everything in
>> just one file.
>
> Maybe the one file could look like:
>
> # cat mon_L3_assignments
> mbm_total_bytes: exclusive
> mbm_local_bytes: shared
> mbm_read_only: unassigned
>
> with new lines appearing when mkdir creates new events, and the obvious
> write semantics:
>
> # echo "mbm_total_bytes: unassigned" > mon_L3_assignments
>
> to make updates.

Yes. That would work.  Also we could move the file to group's main directory like we have other files already.

#cat /sys/fs/resctrl/test/mon_L3_assignments
 mbm_total_bytes: 0=unassigned; 1=unassigned
 mbm_local_bytes: 0=unassigned; 1=unassigned

To assign mbm_total_bytes config on domain 0.

$echo "mbm_total_bytes: 0=exclusive " > mon_L3_assignments

To assign mbm_total_bytes config on all the domains.

$echo "mbm_total_bytes: *=exclusive " > mon_L3_assignments

#cat /sys/fs/resctrl/test/mon_L3_assignments
 mbm_total_bytes: 0=exclusive; 1=exclusive
 mbm_local_bytes: 0=unassigned; 1=unassigned

>
>> Not sure about mbm_assign_control interface as there are concerns with
>> group listing holding the lock for long.
>>
>> -----------------------------------------------------------------------
>> Second phase, we can add support for "mkdir"
>>
>> 1. mkdir info/L3_MON/counter_configs/mbm_read_only
>>
>> 2. mkdir option will create "event_filter" file.
>>     info/L3_MON/counter_configs/mbm_read_only/event_filter
>>
>> 3. Users can modify event configuration.
>>     echo LclFill > info/L3_MON/counter_configs/mbm_read_only/event_filter
>>
>> 4. Users can assign the events
>>
>>    echo mbm_read_only > test/mon_data/mon_L3_00/assign_exclusive
>>
>> 5. Events can be read in
>>
>>     test/mon_data/mon_data/mon_L3_00/mbm_read_only
>
> Is there a matching "rmdir" to make this go away again?
>

I would think so.

Thanks
Babu